Intracellular Polymer Substances Induced Conductive Polyaniline for

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Intracellular Polymer Substances Induced Conductive Polyaniline for Improved Methane Production from Anaerobic Wastewater Treatment Qian Hu, Na Zhou, Kedong Gong, Haoyu Liu, Qing Liu, Dezhi Sun, Qiang Wang, Qian Shao, Hu Liu, Bin Qiu, and Zhanhu Guo ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b05847 • Publication Date (Web): 24 Feb 2019 Downloaded from http://pubs.acs.org on February 24, 2019

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ACS Sustainable Chemistry & Engineering

Intracellular Polymer Substances Induced Conductive Polyaniline for Improved Methane Production from Anaerobic Wastewater Treatment Qian Hu1, Na Zhou1, Kedong Gong1, Haoyu Liu1, Qing Liu1, Dezhi Sun1, Qiang Wang1, Qian Shao2, Hu Liu,3,4 Bin Qiu1*, and Zhanhu Guo3* 1Beijing

Key Laboratory for Source Control Technology of Water Pollution, College of

Environmental Science and Engineering, Beijing Forestry University, Beijing, 100083 China 2College

of Chemical and Environmental Engineering, Shandong University of Science and Technology, 579 Qianwangang Road, Huangdao District, Qingdao 266590, China 3Integrated

Composites Laboratory (ICL), Department of Chemical and Biomolecular

Engineering, University of Tennessee, 1512 Middle Dr, Knoxville, TN 37996 USA 4 Key

Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of

Education; National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou, 450002, China

*: to whom the correspondence should be addressed

[email protected] (B. Qiu) [email protected] (Z. Guo)

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ABSTRACT Intracellular polymer substances (IPS) from bacterial cells were used as a novel template to synthesize porous structured polyaniline (PANI) in this study. The specific surface area of the IPS-induced PANI was ~1.8 times of the pristine PANI. The dosage of the bacterial cell was optimized at an optical density (OD) of 0.536. A conductivity of ~3.1 S/cm was achieved for the IPS-induced porous PANI and was about 4 times higher than that of the PANI synthesized without templates. The improved crystallinity, decreased d-spacing and lower band gap were disclosed to contribute together to the improved conductivity of the IPS-induced PANI. This porous PANI was used as a conductive medium to improve the electron transfer among anaerobic microorganisms, and thus accelerated to produce methane (CH4) gas from wastewater. The IPS-induced PANI with the conductivity ranging from 0.7 to 3.1 S/cm was found to have a positive influence on the production of CH4.

KEYWORDS: Polyaniline, Bacteria cell, Conductivity, Methane production, Intracellular Polymer Substances.

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INTRODUCTION Wastewater discharged from various industries, such as coke plants,1 pharmaceuticals,2 textiles,3 distilleries,4 and wineries,5 always contains organic pollutants at high concentrations. Aerobic bio-processes are commonly employed to treat wastewater, where organics are considered as waste, and was degraded to CO2.6 In these bio-treatments, aeration is required and accounts for ~60% of total power consumption in the wastewater treatment plant. Recently, the organic pollutants in wastewater have been considered as one of the important energy sources.7 The transformation of the organics to methane (CH4) gas by the anaerobic bio-process has been recognized as an effective method to recover energy from wastewater.6 However, the slow electron transfer between bacteria and archaea in the anaerobic sludge leads to both slow CH4 production and long hydraulic retention time, which are challenges for this technology. In recent years, conductive carbon and iron materials have been found to have the ability to increase the direct transfer of extracellular electrons between bacteria and archaea under anaerobic conditions, accelerating the production rate of CH4 from wastewater.8-10 Conductive polyaniline (PANI) with advantages of easy synthesis as well as stable chemical structure in these environments11-12 has pernigraniline, emeraldine and leucoemeraldine states.13-14 However, it presents good electrical conductivity only in the emeraldine state.15 Conductive PANI has attracted increasing attention recently and been widely used in various fields, such as supercapactors,16 sensors,17 electrochemical devices,18-19 corrosion inhibitors20 and environmental remediation.21-23 Moreover, PANI has also been demonstrated to act as a 3



conductive medium to facilitate the electron transfer between bacteria and archaea, and has resulted in the fast production of CH4 from organic wastewater.24 The porosity and conductivity of PANI are important factors of the conductive materials as these facilitate the attachment of microorganism and the electron transfer between bacteria and archaea. Whether the porosity and conductivity of the PANI influence the CH4 production has not been reported. In order to increase the porosity of PANI, the template method is commonly employed since the structure of synthesized PANI can be easily controlled by the used template. For template-assisted synthesis, the aniline monomers are polymerized and grow around the template surface. Recently, the commonly used templates for synthesizing porous polymer structures can be divided into two major categories: organic copolymers,25 and inorganic colloidal particles.26-30 The usually used organic templates include polystyrene nanoparticles31 and block copolymers.32 At the end of polymerization, the copolymer templates need to be removed by immersing in a certain organic solvent, such as toluene31 or chloroform.32 Some inorganic nanoparticles are extensively used as the hard templates to increase the porosity of PANI, such as SiO233 and zeolite34 nanoparticles. At the end of synthesis, some acidic/alkali solutions are usually used to remove the templates in order to obtain porous structures. However, the template removal not only causes the destruction of the formed structures but also generates metal-containing wastewater.29 Moreover, both Cu2O and MnO2 nanoparticles have also been used as the templates for the fabrication of conductive PANI,26-28 and no further template removal is required. For instance, MnO2 has a high redox potential in the acidic 4


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environment, and thus can be used to oxidize the monomers for the formation of conductive polymers. Moreover, MnO2 can be dissolved and release the Mn4+ in the acidic condition. Thus, after the synthesis, the Mn4+ will be reduced to Mn2+ and is totally removed by washing with deionized water. However, the released Mn2+ into the filtration may cause a secondary pollution. Therefore, a novel template is needed to fabricate the porous PANI without generating metal-containing wastewater. The bacteria contain abundant aqueous intracellular polymer substances (IPS) in the interior of the cell, which can easily leak from the cell when it is broken. The IPS contain more than 90% water, and can be easily dehydrated and shrunk when they are dried, which causes the formation of porous PANI.35-36 What is more, the IPS are mainly composed of proteins, which are reported as a chiral template,37 and can induce the formation of chiral PANI and increase the conductivity of the synthesized PANI.37 In this study, the IPS of E. coli bacterial cells were used as a new soft template to synthesize porous nano-polyaniline (nano-PANI) by an in-situ chemical oxidization polymerization method for the first time. The objectives of this paper are to clarify the effects of the IPS of bacteria on the porosity and conductivity of the synthesized PANI. The mechanisms involved in the improved porosity and conductivity are disclosed as well. Porous PANI was used as an electron aisle to improve the electron transfer between bacteria and archaea in an anaerobic wastewater treatment system. The effects of the porosity and conductivity on the CH4 production were investigated as well. 5



MATERIALS AND METHODS Materials. Aniline (C6H7N, 99.7%), ammonium persulfate (APS, (NH4)2S2O8, 99.7%) and hydrochloric acid (HCl, 38%) used as the monomer, oxidant and acid for preparing PANI were obtained from Sigma Aldrich. Diiodomethane, acetone and ethylene glycol used for the detection of contact angle and surface energy of PANI were also purchased from Sigma Aldrich. The E. coli used in this study were collected from the waste competent cells in our lab. Preparation of porous PANI. Porous PANI was fabricated by a chemical oxidation polymerization method. Briefly, desired E. coli bacteria were added into 50 mL deionized water, the optical density (OD) values of the bacteria solution were adjusted to 0.276, 0.536, 0.833 and 1.362. The measured OD at a wavelength of 600 nm represented the biomass in the solution. 1.6 mL aniline was injected into the bacteria solutions. The mixtures were stirred for half an hour at 600 rpm at 0 oC. The solution (50 mL) containing HCl (360 mM) and APS (36.0 mM) in deionized water was added dropwise into the bacteria solution. The E. coli bacteria can be easily destroyed by the highly oxidative APS solution, releasing the IPS. The aniline was polymerized with the IPS for ~2 hours. Then the oligomers in the PANI were removed by using acetone, and the PANI solid products were collected by vacuum filtration. Characterization of porous PANI. A Hitachi S-4800 scanning electron microscopy (SEM) was used to observe the morphology of the IPS-induced PANIs. Before the SEM measurement, the solid samples were coated by a gold layer with a thickness of about 5 nm for better imaging. The porosity was analyzed by a specific surface area instrument (Quanta 6


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Chrome Nova 2200e) at -195.75 oC. Before the measurement, the samples were pretreated under the following conditions: degassing at 100 oC for 12 hours at 0.01 mbar. The specific surface area and pore size distribution of PANIs were obtained by the Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) models. The functional groups were detected by a Bruker Inc. Vector 22 FTIR spectrometer, which was equipped with an ATR accessory spectroscopy, in the range of 400 to 4000 cm-1 at a resolution of 4 cm-1. The conductivity of the synthesized PANI was measured by a four-probe conductivity instrument (ST2258C, Suzhou Jingge Electronic Co., LTD). Before this measurement, the PANI samples were pressed into pellets with a diameter of 2 cm and a thickness of ~1 mm under the pressure of 10 tons. The XRD spectra were obtained using a powder X-ray diffractometer (XRD, Shimadzu, XRD-7000) at a scan rate of 6o/min. UV-vis spectra of PANI samples were measured by a U3010 spectrophotometer (Hitachi, Japan) from 300 to 900 nm. The circular dichroism (CD) was conducted by a JASCO 815 CD spectrometer. Before the UV-vis and CD tests, the solid PANI was dissolved in M-cresol. The viability of bacterial population in the sludge samples was evaluated by a confocal laser scanning microscope (CLSM). Before the measurement, the sludge samples were pretreated by the SYTO® 9 and propidium iodide (PI). The proportions of the live cells and dead cells in the sludge samples were analyzed by the Auto-PHLIP-ML and Image software. Methane production. The CH4 production was conducted by a batch experiment as described in our previous work.38 In brief, 600 mg synthesized porous PANI was added into 7



300 mL anaerobic sludge (SS: 7.65 g/L), then 500 mL nutrient solution (COD: 2000 mg/L) was added. The dissolved oxygen in the mixed solution was removed by fluxing nitrogen gas for 30 minutes in order to reach anaerobic condition. The control experimental group was also conducted in the same way but without adding the conductive PANI. The aluminum foil bag was used to collect the biogas produced from the anaerobic system. The wastewater in the reactor was sampled at every two hours in the first twelve hours and the twenty-fourth hour. The concentration of COD in the solution was examined using EPA-approved Hach testing reagents with a DR3900 spectrophotometer and a DRB-200 reactor. The concentration of CH4 was detected by gas chromatography (GC 7890A, Agilent) installed with a flame ionization detector (FID). For this detection, the carrier gas was nitrogen and the equilibrium gas was a mixture gas (90% Ar/10% CH4). RESULTS AND DISCUSSION Porosity of IPS-induced PANI. The IPS-induced PANI nanoparticles are observed to be like fibers (Figure 1), which are different from the spherical morphology of pristine PANI synthesized without adding E. coli bacteria (Figure S1). No obvious morphological difference was observed between the IPS-induced PANIs synthesized by using different dosages of E. coli bacteria. The diameter of IPS-induced PANI with a bacteria dosage at OD = 0.276 was ~20 nm, and it increased with creasing the bacteria dosage. Figure 1

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The nitrogen adsorption/desorption isotherm was used to determine the porosity of the PANIs. The IV type isotherms indicated the mesopores of the synthesized PANIs (Figure S2). The calculated specific surface area and pore volume of the PANIs were obviously increased when the E. coli bacteria were added in the synthesis system. When the concentration of E. coli bacteria was controlled at OD=1.362, the obtained specific surface area of 51 m2/g and a porous volume of 0.298 cm3/g for the porous PANI were ~1.8 times and 1.5 times that of the pristine PANI (28.2 m2/g and 0.1941 cm3/g, respectively) (Table 1). The specific surface area was also higher than that of the PANIs synthesized using polystyrene (20.57 m2/g),39 polyethylene (30 m2/g)40 and Cu2O (32 m2/g)41 as the templates, while it was lower than those synthesized by some inorganic templates, e.g. MnO2 (110 m2/g),42 SiO2 (201 m2/g)43-44 and MoS2 (205 m2/g).45 Table 1 Figure 2 shows the synthesis pathway of IPS-induced porous PANI. The aniline monomers were attached on the E. coli bacteria by the active –OH and –NH2 groups on the bacterial cell membrane (Figure S3). The proteins were detected as the main component of the released IPS (Ex/Em = 345/225 and 350/275 in Figure S4) when APS was added to the bacterial solution. This indicated that the IPS was released from the E. coli cells upon oxidation by APS. The APS with a concentration of 36.0 mM has a high oxidation state, and can easily destroy the altered cell walls and cell membrane of E. coli bacteria, which causes the release of IPS. During the synthesis of porous PANI, the released IPS existed as the colloid form in the acidic solution due to the contained hydrophobic proteins, and small beads were formed under the 9



stirring condition. However, the formed small protein beads contained more than 90% water. The aniline was polymerized around the protein beads by chemical oxidation, forming the bead@PANI composites. The formed PANI nanorods under a fast stirring condition were different from the PANI nanoparticles synthesized without adding the E. coli bacteria. The bead of proteins had a crucial effect on the properties of the PANIs. The fiber morphology of the synthesized IPS-induced PANI primarily depended on the linear glycoprotein, which was the main content of the IPS.46 After polymerization, the bead@PANI composites were dried in a vacuum oven, the water in the bead core was removed via dehydration and the proteins were shrunk as well. This resulted in the formation of porous structure. Thus, the released protein liquid beads from the E. coli bacteria acted as a soft template for the formation of porous PANI. In this synthesis, the pore formed after water was evaporated. As shown in elements mapping images (Figure S5), all the C, N and O elements were detected in both the pristine PANI and IPS-induced PANIs. However, 2.11% of O was detected in the IPS-induced PANI, which was higher than the 0.56% in the pristine PANI. This was due to the abundance of oxygen in the proteins. It indicated that the proteins remained in the porous PANI. The proteins accounted for less than 1 wt.% of the porous PANI, therefore no further treatment was needed for removing the template. Figure 2 Conductivity of IPS-induced PANI. The conductivity of porous PANI was obviously higher than that of the pristine PANI synthesized without the template (Figure 3). For example, 10


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when the E. coli bacteria was controlled at OD=0.536, the achieved conductivity of 3.1 S/cm was much higher than 0.8 S/cm for the pristine PANI synthesized in this study and the reported PANI (0.5 S/cm) synthesized by the interfacial polymerization method.47-49 This conductivity was also higher than the reported porous PANI synthesized by using the organic and inorganic templates, e.g. polyethylene (0.016 S/m),39 bovine serum (0.72 S/cm),35 and SiO2 (0.14~0.16 S/cm).43-44 As shown in the circular dichroism measurement (Figure S6), the detected characteristic peak at ~475 nm indicated the chirality of the IPS-induced PANIs. The proteins in the IPS bead acted as a chiral template and improved the chirality, resulting in the increased conductivity of the IPS-induced porous PANI.37 Figure 3 The mechanism was elucidated by the FT-IR, XRD and UV-Vis spectra. As shown in Figure 4A, the characteristic peaks located at 1566 and 1483 cm-1 were assigned to the stretching vibration of C=C in N=Q=N (Q stands for quinoid ring) and N–B–N (B stands for benzenoid ring),50-52 respectively. However, the related characterized peaks of the stretching vibration of C=C in N=Q=N and N–B–N shifted to higher wavenumbers (1566 and 1483 cm1,

respectively) in the IPS-induced porous PANI, indicating the interaction between the IPS and

the PANI.53 Moreover, the equal ratio of absorption peak area around 1483 and 1566 cm-1 of the IPS-induced porous PANI indicates the main emeraldine state of the IPS-induced PANI, which determines the good conductivity of the synthesized porous PANI. Figure 4 11



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XRD patterns can be used to characterize the crystallinity and band gap of the PANI materials.54 Figure 4B shows the XRD patterns of the IPS-induced porous PANIs and pristine PANI. The clearly observed crystalline peak near 25o belongs to the (110) plane of crystalline PANI. The peak at around 20o corresponding to the (100) plane also represents the characteristic distance between the ring planes of benzene in adjacent chains.37 However, the peak at ~25o indicated the periodicity perpendicular to the PANI chain.55-56 The presence of peaks indicated the crystallinity of porous PANI. The crystallinity of the PANIs has been calculated (the calculation details was provided in the Supporting Materials) and listed in Table 1. The crystallinity of the IPS-induced PANIs ranged from 53.92% to 68.53% was much higher than 50.23% of the pristine PANI. The crystallinity affects both the intermolecular mobility and the hopping in the PANI chains. The interatomic spacing (d) of the crystalline PANI corresponds to the main peak at a 2θ of ~25o. In this study, the d-spacing of all PANI and porous PANIs was calculated by Bragg’s law, as shown in Equation (1), using the peak at 2θ of ~25o in the XRD pattern.57 nλ=2dSinθ

(1)

where n is an integer, λ is the wavelength of the X-ray and is 1.54 Å for Cu target, and θ is the angle between the rays incident upon and reflected from the PANI samples. As shown in Table 1, the d-spacing was decreased when the IPS of the E. coli bacteria were used as the template. The smallest d-spacing, of 3.46 Å was obtained when the concentration of E. coli bacteria was controlled at OD= 0.536. This indicated that a smaller d-spacing contributed to a higher 12


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conductivity of the IPS-induced porous PANI. The decreased d-spacing was beneficial to increase the hopping probability of charge carriers, resulting in a better conductivity of the IPSinduced PANI.58 The higher crystallinity and smaller d-spacing contributed to the increased conductivity of the porous PANI. The conduction band comprises the π* orbital band and the valance band includes the π orbital.59 The bandgap difference between these two bands determines the optical properties of the conductive PANI.60 Figure 4C shows the UV-vis absorption spectra of the porous PANI. The peak at ~330 nm was related to the π-π* transition.59, 61 The peaks at 450 and 820 nm indicated the polaron/bipolaron transition in PANI, which was protonated by acid during its polymerization.62 As documented, the band gap for the π-π* transition of the PANI was calculated by Equation (2) using the peak intensity at ~330 nm.58

∆E =

ℎ𝑐 𝜆

(2)

where ∆E is the calculated band gap energy of the PANI, h is the Plank’s constant (6.625×10-34 J∙s), c is the velocity of light (3×108 m/s) and the λmax is the wavelength of the absorption maxima according to the first absorption band at 300-500 nm. As shown in Table 1, the band gap of the IPS-induced PANI was obviously lower than that of the pristine PANI. For example, a smaller band gap of 4.42 × 10-19 J was calculated for the IPS-induced porous PANI when the concentration of E. coli bacteria was controlled at OD=0.536. The lower band gap could make the π-π* electronic transition easier, leading to a higher conductivity. This result was consistent 13



with the conductivity of porous PANI. Based on the above discussion, both smaller d-spacing and lower band gap contributed to a higher conductivity of the porous PANI, and a concentration of E. coli bacteria at OD=0.536 was suggested as the optimized dosage for improving the crystallinity and conductivity of the porous PANI. Bio-affinity of IPS-induced PANI. The average contact angle of porous PANI was measured with water, ethylene glycol and diiodomethane. As shown in Figure S7, the contact angle of PANIs with water increased with increasing the concentration of released proteins. When the concentration of E. coli bacteria was controlled at OD=1.362, the contact angle of IPS-induced PANI with water reached 65.85o, which was much higher than the pristine PANI (43.95o). This indicated that the porous PANI had a hydrophilic surface. Moreover, the proteins remaining in the PANIs were highly hydrophobic after being dried, which led to the increase in hydrophobicity of the IPS-induced PANI. The surface energy values of the pristine and IPSinduced PANIs were calculated (refer to the detailed calculation in Supporting Materials) and listed in Table S1. The factors (γ+ and γ-) are non-additive parameters, which are the Lewis acid-base (polar) part of the surface energy of the IPS-induced porous PANIs.63 The acquired values of γ- represent the -NH- in the PANI chains, which serve as electron donors.63-64 This result was consistent with the observation that a higher conductivity was achieved when the concentration of E. coli bacteria was controlled at OD=0.536. Moreover, the surface energy of porous PANI synthesized by using the IPS released from E. coli bacteria as the template was higher than that of the pristine PANI (surface energy65-66 γ=γLW+γAB). A surface energy of 47.27 14


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mJ·m-2 was detected when the concentration of E. coli bacteria was controlled at OD=0.536. The higher surface energy facilitated its distribution in anaerobic sludge, thus PANI was surrounded by the microorganisms (Figure S8). The CLSM was further used to detect whether the conductive PANI affected the living bacteria in the anaerobic wastewater treatment system. The green and red in the CLSM image represent the live or dead state of cells in the anaerobic sludge. As shown in Figure 5, there was no significant change in the proportion of the live/dead cells in the anaerobic sludge after being mixed with the conductive PANIs, compared with that in the original anaerobic sludge. The relatively stable statistical proportion of the live cells (~80%) indicated that the IPS-induced PANIs have a good bio-affinity with the microbes in the anaerobic system. Figure 5 Improved methane production by IPS-induced PANI. In this study, the IPS-induced conductive PANIs were used as the electron aisle and added into the anaerobic sludge in order to accelerate the degradation of organics and the production of CH4 from the wastewater. The concentration of chemical oxygen demand (COD) was decreased from 2000 to 950 mg/L due to the presence of anaerobic sludge without adding PANI over 24 h (Figure 6A), and ~60 mL methane was produced (Figure 6B). The observed lower COD in the effluent indicated that adding conductive PANIs improved the degradation of organics in the anaerobic sludge. It was interesting that a lower COD (~500 mg/L) remained in the wastewater after the treatment by adding PANIs with a conductivity of 3.1 S/cm. Meanwhile, the production of CH4 from 15



anaerobic system amended with conductive PANIs was obviously higher than the control without adding the PANI (Figure 6B). The 108 mL CH4 produced by the anaerobic system with PANI (3.1 S/cm) was ~2 times that without PANI. Moreover, the CH4 production increased with increasing the conductivity of the PANI. This demonstrated that the IPS-induced PANIs could be used as the conductive medium to accelerate the electron transfer between the bacteria and methanogens in the anaerobic sludge. The organic pollutants were degraded by the bacteria, and generated the volatile fatty acids (VFAs). The VFAs in the anaerobic system were found to be accumulated in the initial stage, then it continuously decreased to ~1 mM (Figure S9). This indicated that the bacteria in all the anaerobic systems added with or without conductive PANI have a high activity. The electrons were also generated during the degradation of organics to VFAs. PANI with a higher conductivity made the electrons transfer easier to the methanogens, resulting in a faster methane production. Moreover, the higher surface energy, the hydrophobic property and the porous structure of the IPS-induced PANI facilitated the microorganism attachment to the PANI surface, which was the key for a direct interspecies electron transfer. However, the methane production (78 mL) from the anaerobic system amended by the PANI with a higher porosity (Figure 6B(e)) was obviously lower than that (111 mL) amended by the PANI with a higher conductivity (Figure 6B(a)). This indicated that the conductivity played a more important role in promoting the CH4 production. Meanwhile, the PANI had a stable structure in the environment, and its conductivity was controllable by the added IPS concentration. Therefore, the IPS released from the bacterial 16


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cells were considered as novel templates for adjusting the porosity and conductivity of PANI, which could improve the energy recovery from the wastewater. The porous conductive PANI had stable chemical and structural properties and a good bio-affinity with the anaerobic microorganisms.24 Meanwhile, nanocomposites filled with other functional nanofillers such as conductive metals or carbons,67-75 these can promote further usage of wastewater for energy application and should be the future studies. Thus, it is supposed to have a long life time in the anaerobic sludge and is a sustainable material in the energy recovery from the wastewater. CONCLUSION The IPS released from E. coli bacteria cells were used as novel templates for the first time to synthesize porous PANI. High conductivity of the porous PANI was achieved when the concentration of E. coli bacteria was controlled at OD=0.536. This increased conductivity was attributed to the higher crystallinity, smaller d-spacing and lower band gap induced by the chiral proteins in the IPS. Moreover, the IPS-induced conductive PANI presented a good bioaffinity with the microorgaisms in the ananerobic sludge. It can be used as a novel conductive medium to accelerate the electron transfer between bacteria and methanogens, improving the production of CH4. The conductivity of PANI was demonstrated to be a more important factor than the porosity on improving the CH4 production by the anaerobic microorganisms. The production of CH4 from the PANI amended anaerobic system was ~2 times that without adding PANI. This improves energy recovery from the wastewater by anaerobic digestion. ■ SUPPORTING INFORMATION 17



Surface energy of liquid used in this study, SEM image of pristine PANI, nitrogen adsorption/desorption isotherms of PANIs, FT-IR spectra of E. coli bacteria, 3D-EEM spectra of released IPS, C, N, O element mapping of pristine and IPS-induced PANIs, contact angle of IPS-induced PANI, distribution of PANIs in the anaerobic sludge, volatile fatty acids concentration. These materials are available free of charge via the Internet at http://pubs.acs.org ■ AUTHOR INFORMATION Corresponding Authors *E-mail: [email protected] (Bin Qiu) *E-mail: [email protected] (Zhanhu Guo) Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS This project is financially supported by the Fundamental Research Funds for the Central Universities (No. 2018ZY09) and the National Natural Science Foundation of China (No. 51608037). REFERENCES (1) Zhao, W. T.; Huang, X.; Lee, D. J., Enhanced treatment of coke plant wastewater using an anaerobic–anoxic–oxic membrane bioreactor system. Sep. Purif. Technol. 2009, 66 (2), 279286, DOI: 10.1016/j.seppur.2008.12.028. (2) Ciabattia, I.; Cesaro, F.; Faralli, L.; Fatarella, E.; Tognotti, F., Demonstration of a treatment system for purification and reuse of laundry wastewater. Desalination 2009, 245 (13), 451-459, DOI: 10.1016/j.desal.2009.02.008. 18


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Tables and Table captions Table 1 The characterizations of the IPS-induced porous PANI with different E. coli bacteria dosage. Pore volume (cc/g) 0.2105

d-spacing (Å)

∆E (10-19 J)

Crystallinity (%)

28.2

Pore diameter (nm) 15.1

3.62

4.93

50.23 ± 1.0

OD=0.276

37.1

16.3

0.2736

3.59

4.48

53.92 ± 1.3

OD=0.536

41.2

17.8

0.2812

3.46

4.42

68.53 ± 0.8

OD=0.833

47.6

18.4

0.2934

3.50

4.76

58.70 ± 1.1

OD=1.362

51.0

18.6

0.2980

3.59

4.78

54.01 ± 0.9

Bacteria dosage

BET surface area (m2/g)

OD=0

25



Figures and Figure captions

Figure 1. SEM images of IPS-induced porous PANI with an E. coli bacteria dosage of (A) OD=0.279, (B) OD=0.536, (C) OD=0.833 and (D) OD=1.362.

Figure 2. Proposed synthesis pathway of IPS-induced porous PANI with an E. coli bacteria as the template.

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Figure 3. Conductivity of IPS-induced porous PANI with an E. coli bacteria dosage of (a) OD=0.279, (b) OD=0.536, (c) OD=0.833 and (d) OD=1.362 and (e) pristine PANI.

Figure 4. (A) FT-IR spectra, (B) XRD spectra, and (C) UV-vis absorption of IPS-induced porous PANI with an E. coli bacteria dosage of (a) OD=0.279, (b) OD=0.536, (c) OD=0.833 and (d) OD=1.362 and (e) without bacteria. 27



Figure 5. CLSM images of the anaerobic sludge amended (A) without PANI, (B) pristine PANI and with IPS-induced porous PANIs with a conductivity of (C) 3.1, (D) 1.4, (E) 1.1 and (F) 0.9 S/cm.

Figure 6. (A) COD concentration and (B) methane production from the wastewater treated by the anaerobic sludge amended with porous IPS-induced PANIs with a conductivity of (a) 3.1, (b) 1.4, (c) 1.1, (d) 0.9, (e) 0.7 S/cm and (f) without PANI.

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Table of Content

Synopsis: IPS released from bacterial cell is used as a green template to synthesize porous and conductive nanoPANI for enhance CH4 production from wastewater.

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Intracellular Polymer Substances Induced Conductive Polyaniline for

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